Micro-fluid ejection devices such as ink jet printers continue to experience wide acceptance as economical replacements for laser printers. Micro-fluid ejection devices also are finding wide application in other fields such as in the medical, chemical, and mechanical fields. As the capabilities of micro-fluid ejection devices are increased to provide higher ejection rates, the ejection beads, which are the primary components of micro-fluid devices, continue to evolve and become more complex and more costly to manufacture.
Conventional micro-fluid ejection heads are designed and constructed with silicon micro-fluid ejection head chips that include both the ejection actuators for ejection of fluids and logic circuits to control the ejection actuators. However, the silicon wafers used to make silicon chips are currently only available in round format because the basic manufacturing process is based on a single seed crystal that is rotated in a high temp crucible to produce a circular bouts that is processed into thin circular wafers for the semiconductor industry.
The circular water stock is very efficient for relatively small micro-fluid ejection head chips relative to the diameter of the wafer. However, such circular wafer stock is inherently inefficient for use in making large rectangular silicon chips such as chips having a dimension of 2.5 centimeters or greater to provide a larger ejection swath dimension. In fact the expected yield of silicon chips having a dimension of greater than 2.5 centimeters from a circular wafer is typically less than about 100 chips from a six inch diameter wafer. Such a low chip yield per wafer makes the cost per chip prohibitively expensive.
In order to provide an ejection swath of greater than 2.5 centimeters, multiple semiconductor substrates may be attached to a fluid reservoir. However, alignment of individual multiple substrates is difficult and time consuming.
Another approach to providing a greater swath dimension is to provide separate substrates for the heaters and logic/driver devices. In that instance, the heater substrates may be made of relatively large, non-semiconductor materials while the logic/driver devices are provided on a semiconductor substrate that is electrically connected to the heater substrate. While this approach overcomes alignment problems associated with multiple substrates, it may require a significantly large number of input/output lines connecting the two substrates. For example, if a non-semiconductor substrate contains 10,000 heaters, 10,000 wiring connections may be required between the logic/driver substrate and the heater substrate in order to address each heater individually.
Accordingly, there is a need for improved structures and methods for making micro-fluid ejection heads, particularly ejection heads suitable for ejection devices having an ejection swath dimension of greater than about 2.5 centimeters.
In one of the disclosed exemplary embodiments, a micro-fluid ejection head is provided that has N actuators on a first substrate and logic capable of driving the N actuators on a second substrate. The first and second substrates are electrically interconnected with less than N electrical connections.
In other exemplary embodiments, each ejection actuator is associated with a diode that may be selected from vertically aligned and laterally aligned diodes. The diodes enable the use of row and column logic devices for activation of actuators with a reduced number of address line connections between the first and second substrates.
An advantage of the exemplary embodiments is that they may provide improved micro-fluid ejection heads of greater dimensions without adversely increasing a number of electrical connections required to activate the actuators. Another advantage of exemplary embodiments is that multiple process steps may be readily combined to provide structures having the reduced number of electrical connections.